Preparation

For tomato-chipotle puree:
Heat oil in large skillet over medium-high heat. Add onion; sauté until very brown, about 6 minutes. Add tomatoes, garlic, and chipotle chiles. Cook 1 minute. Transfer mixture to blender; puree until smooth. Season with salt and pepper. Transfer puree to bowl. Cover and chill until cold.

For avocado puree:
Combine all ingredients in processor; puree until smooth. Season to taste with salt and pepper. Transfer puree to bowl. Press plastic wrap onto surface of puree; chill at least 20 minutes and up to 3 hours.